1. Field of the Invention
The present invention relates generally to marine exhaust components, and more particularly to water jacketed marine exhaust pipes that function to mix exhaust gas and cooling water for the purpose of cooling the exhaust gas so as to prevent heat damage to downstream exhaust components.
2. Description of Related Art
Marine engines are cooled by water which is drawn from the body of water in which the vessel is operating (e.g. ocean, lake, etc.). After having cooled the engine, the water is typically discharged into the exhaust gas stream via a water jacketed exhaust component (a/k/a Water Can) to further cool the engine exhaust. Preferably, the exhaust is cooled as far upstream as possible to reduce thermal stress (i.e. overheating) on the downstream exhaust system components. FIGS. 1-4 depict examples of prior art marine exhaust system water cans. The typical arrangement employs a water jacketed exhaust component 2 having an exhaust pipe 4, a water jacket 6 disposed in surrounding relation with exhaust pipe 4, and a spray ring 8. The water jacketed exhaust component is typically mounted downstream of the turbocharger and receives exhaust gas and cooling water from the marine engine. Exhaust gas, referenced “E”, flows through exhaust pipe 4, and cooling water, referenced “W”, flows through the volume 5 between the outer surface of the exhaust pipe 4 and the inner surface of the water jacket 6 and is ejected via apertures 9 in spray ring 8. Generally, the spray ring 8 contains a plurality of apertures 9 from which the cooling water is ejected under pressure from the water pump in the form of a spray or stream.
The prior art water jacketed exhaust component shown in FIG. 1 was burdened by a number of significant problems, and is not in widespread use. First, the water stream exiting the spray ring was generally streamed along only the outer circumference of the volume of exhaust gas flow as shown in FIG. 1. That spray pattern resulted in a poor mixture of cooling water and exhaust gas and thus poor heat exchange. As a result, the exhaust system components downstream of the tail end of the water jacketed exhaust component 2 were subjected to excessive exhaust gas temperatures. An additional shortcoming present with the prior art water jacketed exhaust component shown in FIG. 1, was corrosion. Specifically, the present inventor determined that narrow band of boundary layer turbulent flow along the inner surface of the exhaust pipe 4 was creating a counter flow that caused cooling water to migrate upstream, i.e. opposite the direction of exhaust gas flow. As a result of this upstream migration of cooling water (typically salt water) exhaust gas chemicals such as hydrogen-sulfide and carbon were chemically reacting with the chloride ions produced from the heated salt water to form acid, including sulfuric acid which became deposited on the inner surface of exhaust pipe 4. Over time, this acid corroded the water jacketed exhaust component. Accordingly there existed a need for an improved water jacketed exhaust pipe that provided a superior mixture of cooling water and exhaust gas, while preventing the upstream migration of cooling water.
In response to those problems in the art, the present inventor provided significant advancements in the art of marine water jacketed exhaust components as shown in FIGS. 2-4. In U.S. Pat. Nos. 5,740,670 and 6,035,633, the disclosures of which are incorporated herein by reference, the present inventor disclosed water jacketed exhaust components wherein the tail end of the exhaust pipe (inner liner) were inwardly tapered to clip the turbulence that occurs along the inner walls so that cooling water would not migrate upstream thereby significantly reducing corrosion of the exhaust pipe. In addition, the tail end of the water jacket (outer shell) was inwardly tapered so as to direct and deflect cooling water into the exhaust gas stream thereby improving heat transfer between the hot exhaust gas and the cooling water. Finally, a backward inclined or angled spray ring was disclosed whereby cooling water could be directed toward the outer shell such whereby a portion of the water would be deflected back toward the outer surface of the exhaust pipe, while the remaining portion flowed along the inner surface of the outer shell. The redirected water particles are easily vaporized and in the process, extract a significant amount of heat from the exhaust gases. In addition, the prior art reveals water cans having forward inclined spray rings for directing water downstream and radially inward.
As used herein the term “backward inclined”, in the context of spray ring structure, means that portion of the spray ring structure that projects in a radially outward and upstream (relative to cooling water flow) direction as shown in FIG. 3. Similarly, the tem′ “forward inclined”, in the context of spray ring structure, means that portion of the spray ring structure that projects in a radially outward and downstream direction as shown in FIG. 4.
In addition, FIG. 5 illustrates a known prior art water can manufactured by DeAngelo Marine Exhaust, Inc. in Ft. Lauderdale, Fla. The DeAngelo water can has a forward inclined spray ring with a first series of peripheral notches defining a first set of passageways and a second series of apertures, disposed radially inward from said notches, defining a second set of passageways.
Water jacketed exhaust components incorporating the many advancements developed by the present inventor and disclosed in the '670 and '633 patents have met with widespread success and use in the marine industry and are believed to represent the current state of the art. Marine engines, however, operate over a wide power range, e.g. from idle (low RPM) to full throttle (high RPM), and the respective volume flow of cooling water and exhaust gas produced by a marine engine generally varies in direct proportion to throttle setting, with minimal volume flow of cooling water and exhaust gas at idle, and a maximum volume flow at full throttle. As a result, the water jacketed exhaust components must be sized with particular care in order to perform satisfactorily over all operating ranges.
It has been found that the substantial variations in exhaust gas and cooling water flow rates over the wide range of operating conditions present the exhaust system designer with challenges in sizing a water jacketed exhaust component that performs satisfactorily in operating ranges from idle to full throttle. If the water jacketed component is undersized it will result in excessive raw cooling water backpressure at full throttle that ultimately will result in premature failure of the vessel's water pump. If the water jacketed component is oversized it will result in low cooling water flow velocity, particularly at low RPM, resulting high exhaust gas temperatures. Thus, the water can must be sized with a proper diameter exhaust pipe to maintain desired exhaust gas velocity without creating excessive backpressure on the exhaust side. Furthermore, the water can must be sized with a proper number, size, and location of spray ring apertures to create adequate exhaust gas cooling without creating excessive backpressure on the raw cooling water side.
Accordingly, there exists a need for an improved water jacketed exhaust component that is capable of effectively cooling exhaust gases over a wide range of operating conditions.